DataTypeAttribute.cs

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namespace System.ComponentModel.DataAnnotations;
 
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
public class DataTypeAttribute : ValidationAttribute
{
    private static readonly string[] _dataTypeStrings = Enum.GetNames(typeof(DataType));
 
    public DataType DataType { get; }
 
    public string? CustomDataType { get; }
 
    public DisplayFormatAttribute? DisplayFormat { get; protected set; }
 
    public DataTypeAttribute(DataType dataType)
    {
        DataType = dataType;
        switch (dataType)
        {
        case DataType.Date:
            DisplayFormat = new DisplayFormatAttribute();
            DisplayFormat.DataFormatString = "{0:d}";
            DisplayFormat.ApplyFormatInEditMode = true;
            break;
        case DataType.Time:
            DisplayFormat = new DisplayFormatAttribute();
            DisplayFormat.DataFormatString = "{0:t}";
            DisplayFormat.ApplyFormatInEditMode = true;
            break;
        case DataType.Currency:
            DisplayFormat = new DisplayFormatAttribute();
            DisplayFormat.DataFormatString = "{0:C}";
            break;
        case DataType.Duration:
        case DataType.PhoneNumber:
            break;
        }
    }
 
    public DataTypeAttribute(string customDataType)
        : this(DataType.Custom)
    {
        CustomDataType = customDataType;
    }
 
    public virtual string GetDataTypeName()
    {
        EnsureValidDataType();
        if (DataType == DataType.Custom)
        {
            return CustomDataType;
        }
        return _dataTypeStrings[(int)DataType];
    }
 
    public override bool IsValid(object? value)
    {
        EnsureValidDataType();
        return true;
    }
 
    private void EnsureValidDataType()
    {
        if (DataType == DataType.Custom && string.IsNullOrWhiteSpace(CustomDataType))
        {
            throw new InvalidOperationException(System.SR.DataTypeAttribute_EmptyDataTypeString);
        }
    }
}